Southerly winds carrying warmer more moist air over the extensive snow pack covering the entire Chicago area will make a perfect setup for low gradually thickening clouds to form as the warm air comes in contact with the the cold air just above the snow and condenses. By Saturday evening through the nighttime hours into Sunday it will get a little warmer, but clouds will thicken and fog will form along with some light drizzle. Initially there could be some freezing drizzle on untreated surfaces.
Low pressure developing in the central plains will move east with showers spreading into our area later Sunday night and Monday ahead of the associated cold front. Temperatures will continue to rise through the 40s into the lower 50s here on Monday prior to the cold front passing through later in the day. Colder air will follow on north winds Tuesday.